Pump equipment
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The Roots vacuum pump ZJ-300 (can be rotated easily), equipped with a 5.5KW motor (with an no-load current of 5A); the starting current after installation is 18-20A. What is the reason for this?
As long as there are no mechanical problems while the pump is running, can it be said that a smaller motor could be used? Of course, motor-related issues or problems with the ammeter must first be ruled out
What is the rated current of your 5.5kw motor? 5A even at no load – seems a bit high.
Don’t check to see if it’s overloaded? Overloading isn’t necessarily due to a small motor; it could also be caused by an excessive flow rate
The starting current is about 7 times the operating current, which is normal
It’s normal; the starting current can be several times higher.
The starting current of a motor is 5-7 times the rated current; if the operating current is that high, it is abnormal
The current drawn by a centrifugal pump at the moment it is started is quite high; it’s not clear exactly how many times the rated current this can be. Therefore, electrical switches are equipped with a current overload protection time limit – as long as the pump is started within this time frame, there should be no problems, in my opinion.
This post was last edited by 3983596_FPPZ on 2018-12-6 at 22:13. A high starting current is normal, usually being 7 times the normal current. Different pump types have varying startup times due to factors such as differences in moment of inertia and density of the fluid. It is necessary to use a time delay relay for electrical protection; generally, a delay of around 15 seconds is set, depending on the equipment’s startup time, in order to prevent tripping caused by the high current during startup and thus ensure successful startup
This pump cannot be started on its own; a vacuum level of above -0.095 MPa is required for startup. It’s likely that you haven’t installed a pre-stage pump, or the vacuum level achieved by the pre-stage pump is not sufficient to meet the startup conditions of the rotary vane pump. As a result, the current level becomes extremely high and the temperature of the pump body rises; forced use of the pump will soon lead to damage to the motor as well as the pump itself
When the vacuum level of the primary water circulation pump reaches -90 kPa, the secondary pump starts automatically; however, when the current drawn by the secondary pump reaches 18–20 A, the pump shuts down.